Portable shelters have been in existence since prehistoric time, but the modern era has seen an increasing need for greater sophistication in the quality and type of construction for portable shelter devices. In the last twenty to thirty years, the quick erect shelter industry has dramatically grown as the result of new technologies and fabrics. Support structures and design, especially in the field of light-weight tents and mountaineering shelters, have witnessed dramatic improvements. These developments manifest themselves in special application fields, but relatively little attention has been paid to the development of larger area shelters that are stored in a small collapsed state but which may be expanded with a minimum amount of effort into sturdy, large area shelters.
One response to this need is described in my U.S. Pat. No. 4,641,676. This patent shows a portable canopy structure having a framework that may be collapsed into a stored state yet which may be expanded and erected for use. The framework includes a plurality of upright support members which are interconnected by a plurality of scissor assemblies. The scissor assemblies have their upper outer ends fastened to the upright supports by removable mounts. The lower outer ends, however, are secured to a sliding mount which travels along the upright member between the erect and collapsed states. Internal scissor assemblies may be provided to support a central post, and a covering extends across the tops of the supports and is supported by the posts in a dome-like manner. This structure is also similar to that described in U.S. Pat. No. 4,607,656 issued Aug. 26, 1996 to Carter.
While the structures shown in my '676 Patent and in the Carter Patent do provide significant advantages over earlier structures, especially in the relative ease of both expansion and collapse, they nonetheless have some drawbacks. For example, in use, the scissor assemblies shown in these two structures are under compressive forces. When the scissor assemblies are subjected to forces transversely of their plane, the combination of this force with the compressive force can result in substantial bowing of the scissor assemblies and distortion of the canopy framework.
The structure described in my '676 Patent was modified by that disclosed in my U.S. Pat. No. 4,779,635 issued Oct. 15, 1988. In this patent, the canopy structure outwardly biased its corner support members so that the framework interconnecting the adjacent corner support members was placed in tension as opposed to compression. Nonetheless, the assembly shown in my '635 Patent was still subject to improvement in the scissor bar interconnections.
In an effort to enhance the stability of scissoring canopy frameworks, I developed the structures shown in my U.S. Pat. No. 5,244,001. In this patent, socket-type mounts were employed to fasten the ends of the scissor assemblies to the upright supports and to each other. The sockets provided by the mounts were formed to have spaced-apart, parallel side wall portions. The end scissor assemblies had outer end portions of rectangular cross-section so that each could be received in a close-fitted engagement between the parallel side wall portions thereby forming planar contact surfaces. The socket both simplified interconnection of the various structural members while at the same time provided resistance to lateral forces.
Despite the improvements taught in the above-noted patents, there remains a need for improved framework structures that provide quick erect canopy shelters. For example, the canopy frameworks disclosed in the above-referenced patents each utilize one rigid bracket and one slide bracket on the upright supports. The use of a slide bracket is necessary to allow a pair of upper and lower outer ends of the scissor assemblies to move apart from one another thereby allowing the scissor assemblies to move between the expanded state and the collapsed state. The present invention has been designed to eliminate the need for a slide bracket so that the ends of the scissor assemblies may each be secured to the upright supports at a fixed location.